Pig iron refining process

ABSTRACT

Pig iron is refined in a tiltable convertor using oxygen blown into the melt with a surrounding sheath of protective fluid such as propane, the metal is blown in two stages, first with the vessel in a vertical position and then with the vessel on its side. The first blow is stopped when the carbon is not more than 0.50%, preferably about 0.20-0.30%, above the desired final carbon.

United States Patent Nilles Dec. 24, 1974 [54] PIG IRON REFINING PROCESS 2,875,037 2/1959 Wright 75/60 3,313,619 4/1967 Decamps. 75/60 [75] Inventor- Embourg 3,330,645 7/1967 Moustier 75/60 Belglum 3,706,549 12 1972 Knuppel 75/60 Assigneei fisenWelrke-gesellschaft FOREIGN PATENTS OR APPLICATIONS aximi ians utte m.b.H

4 1 Sulzbach-Rosenberg, Germany 8 7,1966 France 75,60

[22] Filed: Apr, 3, 1973 Primary ExaminerC. Lovell Assistant ExaminerPeter D. Rosenberg [2H Appl' 347521 Attorney, Agent, or FirmLawrencc 1. Field [30] Foreign Application Priority Data [57] ABSTRACT Apr. 4, 1972 Belgium 782186 Pig iron is refined in a tiltable convertor using oxygen blown into the melt with a surrounding sheath of pro- [52] US. Cl. 75/60, 75/59 tective fluid such as propane, the metal is blown in [51] Int. Cl. C2lc 5/34 two stages, first with the vessel in a vertical position [58] Field of Search 75/60, 59 and then with the vessel on its side. The first blow is stopped when the carbon is not more than 0.50%, [56] References Cited preferably about 0.20O.30%, above the desired final UNITED STATES PATENTS Savard 75/60 carbon.

7 Claims, 2 Drawing Figures PATENTED BEE24B974 ll Illllli'll'lllllllllii PIG IRON REFINING PROCESS The present invention relates to a pig iron refining process and more specifically to refining phosphorus containing pig iron in a tiltable refining vessel.

Among the various pig iron refining processes used in industry and making use of pure oxygen, a process was recently developed in which refining oxygen is blown into a converter through its bottom, the protection of the latter being provided by an appropriate fluid surrounding the oxygen jet(s) passing through the bottom, for example, as described in US. Pat. No. 3,706,549, issued Dec. 19, 1972.

More recently, the blowing of oxygen into the molten pig iron in the converter through one or more side tuyeres located in the lateral wall of the converter and below the normal upper level of the liquid metal has been proposed instead of being located in the converter bottom. In this process, the refining gas is blown through one or more tuyeres in the converter side wall and the jet of refining gas is surrounded by a fluid protecting the converter lining against the corrosive action of the oxygen jet at the region where it discharges into the melt.

The object of the present invention is a pig iron refining process and specifically for refining phosphorus pig iron, which is carried out with a tipping converter equipped with at least one side tuyere having dual, coaxial conduits.

The process of the present invention comprises a first stage consisting of: (l charging the converter with liquid iron, with scrap iron and advantageously with lime in powder or blocks; and (2) blowing a highly oxidizing gas which may contain powdered slag forming agents through the central conduit of the side tuyere(s), and in blowing simultaneously a protective fluid through the peripheral tube of the tuyere(s), both fluids discharging below the upper level of the liquid metal surface, during a first stage in which the converter is substantially vertical. This procedure is continued until a carbon content close to the desired final one is achieved.

In a second stage, after the converter has been tilted to a substantially horizontal position so that the outlet of the side tuyere(s) are located above the metallic bath, blowing is performed through the central conduit of the side tuyere(s) in the side wall and onto the metal bath with a highly oxidizing gas jet capable of penetrating the slag and the metal through the slag while simultaneously blowing a protective fluid through the pe ripheral conduit of the said tuyere(s). By this procedure, very considerable de-phosphorisation can be achieved for a metal still containing as much as 0.1% to 0.8% C, depending on the analysis to be produced.

In the drawings accompanying this application:

FIGS. 1 and 2 are schematic representations of the first and second stages of the process described above showing the convertor in a vertical position and in a horizontal position, respectively. It will be understood that the tipping convertor can be further tilted for dis charging the contents of the convertor after refining is completed.

The invention will be more fully understood from the Examples which follow which are intended to illustrate the invention and are not intended to limit it in any way.

EXAMPLE I A pig iron containing 3.6% C, 0.3% Si, 0.3% Mn and 1.8% P, balance Fe except for incidental impurities was charged into a 35 ton convertor. The melt was at about l,240C. The charge consisted of 29 tons of the stated pig iron, 10 tons of scrap, 2.7 tons of powdered lime and 200 Kg. of colemanite as a flux.

The oxygen blow is as follows: a. In a first phase with the convertor vertical, 1,30 Nm were blown in through a side tuyere at the rate of Nm lmirr, for 13 minutes. The oxygen was introduced through a high chromium steel pipe. The oxygen stream was shielded by 3.6 Nm of propane blown in as a jacket around the oxygen, through a larger pipe concentric with the oxygen pipe, at a flow rate of about 3.6

Nm /min.

At the end of this phase the carbon content was lowered to 0.75% and the phosphorus was lowered to 0.20%. About 8% of iron was converted to iron oxide which passed into the slag.

b. The convertorwas tipped to the horizontal position and in the second phase, lasting for about 6 minutes 290 Nm of oxygen was blown in at a rate of about 50 Nm /min, simultaneously with about 9 Nm of propane blown in at about 1.5 Nm /min. Then about 300 Kg of ore was added for cooling of the melt.

The final metal analyzed 0.575%C and 0.026%P, and had a temperature of about 1,62.0C. Approximately 24% of the iron was oxidized and recovered as slag.

EXAMPLE 11 Using a convertor with a capacity of 47 tons and a starting hematite pig iron containing 4.5% C, 0.87% Si, 0.6% Mn, 0.15% P, balance Fe, at a temperature of 1,3 80C, the convertor was charged with the following:

37.5 tons hematite pig iron 2.5 tons powdered lime 9 tons light scrap 200 Kg of colemanite and into the melt oxygen was blown through the side of the vessel through a compound tuyere, at a rate of about Nm lmin. for about 14 minutes, or until about 1,850 Nrn of 0 were blown. into the melt, simultaneously with the introduction of oxygen about 50 Nm of propane was blown into the melt, at the rate of about 3.5 Nm lmin. The convertor was turned to the horizontal position, with the melt then analyzing 0.85% C and 0.026% P, and 6% Fe in the slag.

With the convertor in this position, oxygen surrounded by propane, Nm of oxygen at the rate of 50 Nm /min. and 4.5 Nm of propane at the rate of 1.5 Nm /min. were blown in simultaneously for about 3 minutes after which 200 Kg light scrap was added for cooling.

The resulting product contained 0.6% C and 0.012% P and had a temperature of about. 1,610C. About 9% iron was oxidized in the slag.

1 claim:

1. A pig iron refining process in a tipping converter of which the side wall is provided with at least one tuyere consisting of two coaxial conduits, the central conduit being for the blowing in of a highly oxidizing gas and the peripheral conduit being for the introduction of a protective fluid through the converter wall into the melt in said converter, which comprises:

1. loading the converter with liquid iron and with scrapiron,

2. putting the converter in an essentially vertical position,

3. blowing in a highly oxidizing gas through the central conduit of the side tuyere(s) simultaneously with the blowing in of a protective fluid through the peripheral conduit of said side tuyere(s) said tuyere discharging said oxygen and said protective fluid below the upper level of the metal bath,

4. continuing the blowing until a carbon content which is approximately the desired one has been achieved, and

5. thereafter placing the converter in an essentially horizontal position so that the outlet of the side tuyere(s) is located above the metal bath level, and thereafter completing the refining by blowing in a highly oxidizing gas which penetrates the slag and the metal through the slag through the central conduit of the side tuyere(s) simultaneously with the introduction of a protective fluid into said melt through the peripheral conduitof said side tuyere(s).

2. The process of claim 1 in which the oxidizing gas is oxygen and said protective fluid is propane.

3. The process of claim 1 wherein the pig iron initially contains between about 1% and 2.2% P.

4. The process of claim 1 wherein the pig iron initially contains less than 0.4% P.

5. The process of claim 1 wherein the melt is blown in the first phase to about not more than 0.5% C content than the final carbon content of the metal after all blowing has finished.

6. The process of claim 1 including in addition, loading the converter with lime in addition to the liquid iron and scrap iron.

7. The process of claim 1 wherein the highly oxidizing gas blown in in step (3) contains powdery slag forming agents.

l l l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3,856,510 DATED December- 2 i, 197 i lNvENTORtS) Paul Emile Nilles it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Assignee should be--Eisenwerk Gesellschaft--not"Eisenwerke Gesellschaft" Signed and sealed this 3rd day of June 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A PIG IRON REFINING PROCESS IN A TIPPING CONVERTER OF WHICH THE SIDE WALL IS PROVIDED WITH AT LEAST ONE TUYERE CONSISTING OF TWO COAXIAL CONDUITS, THE CENTRAL CONDUIT BEING FOR THE BLOWING IN OF A HIGHLY OXIDIZING GAS AND THE PERIPHERAL CONDUIT BEING FOR THE INTRODUCTION OF A PROTECTIVE FLUID THROUGH THE CONVERTER WALL INTO THE MELT IN SAID CONVERTER, WHICH COMPRISES:
 1. LOADING THE CONVERTER WITH LIQUID IRON AND WITH SCRAP IRON,
 2. PUTTING THE CONVERTER IN AN ESSENTIALLY VERTICAL POSITION,
 2. putting the converter in an essentially vertical position,
 2. The process of claim 1 in which the oxidizing gas is oxygen and said protective fluid is propane.
 3. The process of claim 1 wherein the pig iron initially contains between about 1% and 2.2% P.
 3. blowing in a highly oxidizing gas through the central conduit of the side tuyere(s) simultaneously with the blowing in of a protective fluid through the peripheral conduit of said side tuyere(s) said tuyere discharging said oxygen and said protective fluid below the upper level of the metal bath,
 3. BLOWING IN A HIGHLY OXIDIZING GAS THROUGH THE CENTRAL CONDUIT OF THE SIDE TUYERE(S) SIMULTANEOUSLY WITH THE BLOWING IN OF A PROTECTIVE FLUID THROUGH THE PERIPHERAL CONDUIT OF SAID SIDE TUYERE(S) SAID TUYERE DISCHARGING SAID OXYGEN AND SAID PROTECTIVE FLUID BELOW THE UPPER LEVEL OF THE METAL BATH,
 4. CONTINUING THE BLOWING UNTIL A CARBON CONTENT WHICH IS APPROXIMATELY THE DESIRED ONE HAS BEEN ACHIEVED, AND
 4. continuing the blowing until a carbon content which is approximately the desired one has been achieved, and
 4. The process of claim 1 wherein the pig iron initially contains less than 0.4% P.
 5. The process of claim 1 wherein the melt is blown in the first phase to about not more than 0.5% C content than the final carbon content of the metal after all blowing has finished.
 5. thereafter placing the converter in an essentially horizontal position so that the outlet of the side tuyere(s) is located above the metal bath level, and thereafter completing the refining by blowing in a highly oxidizing gas which penetrates the slag and the metal through the slag through the central conduit of the side tuyere(s) simultaneously with the introduction of a protective fluid into said melt through the peripheral conduit of said side tuyere(s).
 5. THEREAFTER PLACING THE CONVERTER IN AN ASSENTIALLY HORIZONTAL POSITION SO THAT THE OUTLET OF THE SIDE TUYERE(S) IS LOCATED ABOVE THE METAL BATH LEVEL, AND THEREAFTER COMPLETING THE REFINING BY BLOWING IN A HIGHLY OXIDIZING GAS WHICH PENETRATES THE SLAG AND THE METAL THROUGH THE SLAG THROUGH THE CENTRAL CONDUIT OF THE SIDE TUYERE(S) SIMULTANEOUSLY WITH THE INTRODUCTION OF A PROTECTIVE FLUID INTO SAID MELT THROUGH THE PERIPHERAL CONDUIT OF SAID SIDE TUYERE(S).
 6. The process of claim 1 including in addition, loading the converter with lime in addition to the liquid iron and scrap iron.
 7. The process of claim 1 wherein the highly oxidizing gas blown in in step (3) contains powdery slag forming agents. 